Golf Club Head Having Center of Gravity Offset

ABSTRACT

A wood type golf club includes a face and a hosel with a center of gravity offset. A shaft presents a central axis, and is joined to the wood type club head at the hosel, the shaft presenting an axis projected through the hosel and through the club head. The shaft and hosel present a plane relative to and generally parallel to the face of the club head. The wood type club head has a center of gravity configured within the plane.

BACKGROUND Field of the Invention

The present application is directed to a golf club head, particularly a golf club having a configured center of gravity.

Description of the Related Art

A golf club is made of a grip, a shaft, and a club head. A golf club shaft is typically a tapered tube made of metal or carbon fiber composite. The golf club shaft has a given amount of flex. The shaft flex is the amount that the shaft will bend when placed under a load.

Typical current driver and fairway wood golf club heads are typically formed of lightweight, yet durable material, such as steel or titanium alloys. These materials are typically used to form thin club head walls. The club head is joined to the shaft at a hosel.

The center of gravity configuration of a golf club head is a critical parameter of the golf club's performance. Upon impact, the position of the center of gravity greatly affects launch angle and flight trajectory of a struck golf ball.

Various approaches have been implemented for positioning discretionary mass, thus the center of gravity, about a golf club head. Many club heads have integral sole weight pads cast into the head at predetermined locations to lower the club head's center of gravity. To achieve localized mass, weights formed of high-density materials have been attached to the sole, skirt, and other parts of a club head. Such weights are usually permanently attached to the club head and are limited in total mass. This fixes the club head's center of gravity.

Moreover, golf swings vary among golfers, but the total weight and center of gravity location for a given club head is typically set for a standard, assumed ideal, swing. Thus, even though the weight may be too light or too heavy, or the center of gravity too far forward or too far rearward, the golfer often cannot easily find a club center of gravity to his or her particular swing. Rather, golfers often must test a number of different types and/or brands of golf clubs to find one that is suited for them. Even then later fine adjustments of the center of gravity would be desirable.

It should be appreciated that the ability to position and even adjust the center of gravity location in the club head of golf clubs is useful for controlling performance of the golf club. It would be advantageous to have a system and process which facilitates selecting, positioning, and adjusting center of gravity.

SUMMARY

The present invention is directed to golf club apparatus and processes. A wood type golf club includes a face and a hosel with a center of gravity offset. A shaft presents a central axis, and is joined to the wood type club head at the hosel, the shaft presenting an axis projected through the hosel and through the club head. The shaft and hosel present a plane relative to and generally parallel to the face of the club head. The wood type club head has a center of gravity configured within the plane.

These and other features, aspects, and advantages of the invention will become better understood with reference to the following description, and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a top view of an embodiment according to the current invention;

FIG. 2 depicts a side view of an embodiment according to the current invention;

FIG. 3 depicts a top view of prior art;

FIG. 4 depicts a side view of prior art;

FIG. 5 depicts a side perspective view of an embodiment according to the current invention;

FIGS. 6A-6C depict various configurations of an embodiment according to the current invention;

FIG. 7 depicts club head speed and energy of data;

FIG. 8 depicts club head energy at various configurations of the current invention; and

FIG. 9 depicts an embodiment of a process according to the current invention.

DETAILED DESCRIPTION

Detailed descriptions of the preferred embodiment are provided herein. It is to be understood, however, that the present invention may be embodied in various forms. Therefore, specific details disclosed herein are not to be interpreted as limiting, but rather as a basis for the claims and as a representative basis for teaching one skilled in the art to employ the present invention in virtually any appropriately detailed system, structure or manner.

The center of gravity 18 location in the club head 20 of golf clubs is useful for controlling performance of the golf club. This means that a club head 20 has a vertical center of gravity location, defined by the height on the club head relative to the sole. It also has a horizontal center of gravity location, that is to say how far over it is from the center of the shaft 12 in the hosel 30 of the head. Finally, the center of gravity is also defined by how far back from the club face it is located.

Current drivers have the center of gravity behind the shaft 12 attachment. This causes the shaft 12 to bend forward due to the force couple acting on the club head 20. The centrifugal force, the force up the shaft 12, and the force in the opposite direction acting on the club head 20 center of gravity. This results in a bending moment turning the club head 20 forward. The club head 20 rotates to the left (for a right handed golfer) and upward, effectively giving a higher loft at impact. This forward shaft 12 bend is, in the golf industry, regarded as giving an extra “kick” to the golf ball, defining at a kick point of the shaft 12, as shown in FIG. 3.

In further analysis of the shaft 12 kick, it is observed that the downswing in a golf swing lasts approximately 0.02 seconds. During this time the club head 20 moves about 50 mm forward relative where it would be if the shaft 12 had been perfectly stiff (unbendable). Therefore, the addition to the club head 20 speed is V=50 mm/0.02 s=0.05 m/0.02 s=2.5 m/s=6 mph.

There is also another relevant effect, referred to as the “Hammer” effect in this specification. As the club head 20 makes contact with the ball it will start to slow down. By observation and swing analysis data of professional golfers, it is found that a typical club head 20 pre-impact speed of 114 mph will result in a typical club head 20 post-impact speed of 93 mph. The reduction in speed occurs over a distance of about 4/7 of the diameter of the golf ball. The diameter of a golf ball is 43 mm. Therefore the speed of the club head 20 is reduced from 114 mph (51.0 m/s) to 93 mph (41.6 m/s) over a distance of 25 mm. As the speed is reduced, the shaft 12 will bend less at 93 mph than it did at 114 mph. Let us again assume that a particular shaft 12 bends forward by 50 mm at 114 mph. Assume the shaft 12 bends linearly with the bending forces, the bending forces are proportional to centripetal forces.

F=m×v ² /r

m equals mass and is constant. r equals radius and is substantially constant, with the forward bend X at 93 mph. Therefore 114/93=50 mm/X and X=33 mm.

Therefore the shaft 12 kicks backwards 17 mm (50 mm−33 mm). It does this in the time it takes the club head 20 to travel a distance of 25 mm. The club head 20 is traveling at an average speed of (51.0+41.6)/2=46.3 m/s. The time taken is 0.025 m /46.3 m/s=0.0005 seconds=0.5 milliseconds. This is the duration that the club head 20 stays in contact with the ball. The speed decrease due to the Hammer effect is thereby 17 mm/0.5 milliseconds, or 0.017 m/0.0005 s=34 m/s. The speed is decreasing due to the Hammer effect, effectively linearly during impact. The effect should thereby be halved when calculating the effect it has on effective club head 20 speed. The average effective speed is thereby 34/2 m/s=17 m/s (38 mph)

In the example of the 114 mph club head 20 speed, the effect of the shaft 12 kick is accounted for. That means that in this example the golfer is swinging the club at 108 mph (114−6), which will be further referred to as the swing speed.

The shaft 12 kick is eliminated by disposing the club head's 20 center of gravity to be located in line/collinear with the shaft 12, from the golf club face 26 perspective, as shown in FIG. 1, where the club head 20 presents a first axis generally parallel with the golf club face 26 and collinear with the hosel 30. In alternate configurations, the shaft 12 kick is eliminated by disposing the club head's 20 center of gravity to be located in the plane 14 presented by the shaft 12. In alternate configurations, the shaft 12 kick is eliminated by disposing the club head's 20 center of gravity to be located proximate the plane 14 presented by the shaft 12. In those alternate configurations, the center of gravity may be disposed outside the axis presented by projecting the shaft through said hosel and through said club head.

This can be accomplished by shifting more weight towards the face 26 of the club head 20 or by offsetting the shaft 12 attachment further towards the back of the club head 20, or combination thereof. The club head 20 speed at impact would then be 108 mph as there would negligible or no shaft 12 kick. However, the effective club head 20 speed will be 146 MPH (108+38).

Assuming a given club, strike force, and swing speed of 114 mph the ball will carry about 270 yards. Proportionately, a swing speed of 146 mph typically yield ball carry of about 346 yards, or an increase in distance of about 76 yards.

As the shaft 12 will no longer bend forward or backward in the swing plane, a much higher degree of accuracy is obtained, leading to a more predictable trajectory, that is to say that the ball will remain in the fairway as desired. As the shaft 12 kick is minimized or eliminated, the club head 20 static loft and dynamic loft will be substantially the same. For optimum results, the static loft of the club head 20 should be increased as the static loft equals the dynamic loft. For a traditional club head, the dynamic loft is greater than the static loft. To account for this, a larger static loft is required when the static loft equals the dynamic loft. As the loft is increased, this give opportunity to position more weight low and forward in the face of the club head 20, thereby facilitating alignment of the center of gravity with the shaft attachment to the club.

The further forward the center of gravity is located, the stronger the Hammer effect. If one were to locate the center of gravity forward of the hosel 30, the Hammer effect would be even stronger as the club will kick forward at impact with the ball. The shaft 12 kick effect would then be exhibited. This would have a small negative effect while the dominant effect will still be the Hammer effect. This will lead to further ball carry even, however accuracy will suffer again as the shaft 12 flexes.

The shaft 12 flex can then be optimized by matching the frequency of the fully assembled golf club to the club head 20 speed of the golfer. The optimum club frequency for each swing speed can be obtained by testing. One frequency measuring method known in the art for obtaining the shaft frequency of a shaft is to by locking the grip end of the shaft in a vice and pulling the distal, free club head to the side and releasing it so that it can vibrate freely. A laser beam is used to count the cycles over a time period and gives the resulting frequency in hertz. The higher the frequency, the higher the stiffness of the shaft. The higher the frequency the faster the club head moves. It is within the scope of this invention to use other process or systems known to the art.

When a prior art golf club is swung, the shaft 12 is bending, as the center of gravity of the club head 20 is not aligned with the shaft 12. We are here considering the bending in the plane affecting the dynamic lie angle, as illustrated in the adjacent space apart planes of FIG. 4. The faster the club is swung, the lower the dynamic lie angle at impact becomes. This bending introduces a factor of uncertainty and causes irregular results. To compensate for this effect, the center of gravity can be set inline with the shaft 12 line, as illustrated in the plane of FIG. 2. The shaft 12 is joined to the club head 20 at the hosel 30, with the shaft 12 and hosel 30 defining a second axis. Additionally, the shaft and hosel present a plane 14 relative to the face 26 of the club head 20. In these configurations of center of gravity, the shaft 12 will not bend in any direction when swung. The center of gravity of the club head 20 can be relocated by moving masses when designing the club head 20 as well as by locating the hosel 30 in the required location.

Embodiments of the present invention are directed to method for selecting an optimum center of gravity, a golf club having a club head 20 with an optimum center of gravity, and a golf club with a hosel body 40 permitting user adjustment of the center of gravity of a club head 20. Although the depicted hosel body 40 includes multiple hosels 30 spaced apart, it is within the scope of this invention to include a single hosel 30 at an offset with a configured center of gravity.

It is within the scope of this invention to apply the center of gravity to a newly created golf club or to apply the center of gravity offset to an existing club directly without the use of the above described hosel body 40. FIG. 9 illustrates an embodiment of a process according to the current invention. At step 110, the parameters for a golf club or similar golf clubs is received. Representative received parameters can include club type, shaft length, shaft thickness, club head weight, club head shape, club head composition, club face weight, club head weight distribution, center of gravity position, hosel position, club face position, and other parameters. At step 120, the current center of gravity of the club head is determined. It can be received directly or determined from the received golf club parameters. At step 130, the optimum center of gravity is determined. The first axis of the club head generally parallel to the face and collinear with the hosel is determined. The second axis defined by the shaft joined to the club head is determined. The optimum center of gravity is determined and defined as proximate the intersection of the first axis and the second axis. Alternately, the optimum center of gravity is defined as a plane presented by the shaft 12 and hosel 30 relative to and generally parallel to the face 26 of the club head 20. At step 140, the optimum center of gravity is applied to the golf club. An exemplary manner of doing so is by adding weighted screws to the club head 20. An alternate application of the process includes providing a hosel body 40 with a plurality of spaced apart hosels to be interposed between the club head 20 and the shaft 12, permitting user adjustment of the center of gravity of a club head.

Prior to play, a golfer may seek to adjust a club for directional tendency (direction, as discussed above) or distance, seeking longer or superlong shots. For example, a course may have holes with open fairways and long tees, the golfer may seek a center of gravity which maximizes distance. On the other hand, in a situation such as a tight fairways with “S” curves, directional control may be the higher priority. The hosel body 40 includes an upper surface having a plurality of spaced apart hosels 30 disposed linearly. The exemplary hosels 30 are spaced apart with a range such that there is a hosel 30 position optimized for each priority. As a golfer is not allowed, according to the rules of golf, to alter any club during play, in testing, practice, or other situations, a golfer may adjust the center of gravity.

Testing was carried out with a golf club of the alternate application where the shaft 12 is offset at three different points defining three different centers of gravity, as shown in FIGS. 6A-6C. Test data was obtained using a Swingbyte measuring tool. The energy transferred to the ball is calculated and shown in the figure below. Kinetic energy is calculated as ½ mv², where m is the combined mass of the club head 20 and the device for positioning the shaft 12 in three different locations, total mass is 388 g. club head 20 speed, v, before and after impact is obtained from the primary data from the Swingbyte measuring instrument. Note that the device fixed to the club head 20 made the club head 20 very heavy. This caused a low swing speed. However, one skilled in the art would appreciate the indication of positive effect from the trends shown the results. Raw test measurements are shown in FIGS. 7 and 8.

Insofar as the description above and the accompanying drawing disclose any additional subject matter that is not within the scope of the single claim below, the inventions are not dedicated to the public and the right to file one or more applications to claim such additional inventions is reserved. 

What is claimed is:
 1. A wood type golf club with a center of gravity offset, comprising: a shaft presenting a central axis; a wood type club head having a face and a hosel; said shaft joined to said wood type club head at said hosel, said shaft presenting an axis projected through said hosel and through said club head; said shaft and hosel presenting a plane relative to and generally parallel to said face of said club head; said wood type club head having a center of gravity configured within said plane and outside said projected axis by said shaft to hosel joint.
 2. The golf club of claim 1 wherein the static loft of the club head is substantially equal to the dynamic loft.
 3. The golf club of claim 1 wherein weight is positioned lower and forward in the face of the club head.
 4. The golf club of claim 1 wherein the shaft flex is optimized by matching the frequency of the golf club to the club head speed of a golfer.
 5. The golf club of claim 1 wherein is the center of gravity of the club head is offset by moving masses.
 6. The golf club of claim 1 wherein is the center of gravity of the club head is offset by a configured hosel position.
 7. A process for golf club head center of gravity offset, comprising the steps of: receiving parameters for said golf club head, including dimensions and mass; determining the current center of gravity from said golf club head parameters; projecting an axis presented by said shaft projected through said hosel and through said club head; projecting a plane presented said shaft and hosel relative to and generally parallel to said face of said club head; determining the optimum center of gravity, said optimum center of gravity defined as within said plane and outside said projected axis by said shaft to hosel joint.
 8. The process of claim 7 further comprising the step of applying the center of gravity offset to said golf club.
 9. The process of claim 8 wherein said center of gravity adjustment is accomplished by shifting more weight towards the face of the club head.
 10. The process of claim 8 wherein said center of gravity adjustment is accomplished by offsetting the shaft attachment further towards the back of the club head.
 11. The process of claim 8 wherein said center of gravity adjustment is accomplished by a combination of shifting more weight towards the face of the club head and offsetting the shaft attachment further towards the back of the club head.
 12. The process of claim 12 further comprising optimizing the shaft flex by matching the frequency of the golf club to the club head speed of a golfer.
 13. A golf club accessory comprising: a hosel body having an upper surface and lower surface; said lower surface having a tip for affixing to a club head; said upper surface having a plurality of spaced apart hosels dimensioned for receipt of a shaft, whereby a user can selectively offset the center of gravity of the club head in a series of successively spaced apart planes generally parallel to the club face. 